To preserve certain food products, such as meat or fish, when packaged in containers, brine is added to completely drown the products before the lid is put on. However, some of the lids used to seal the containers are so shaped that they allow air to be trapped inside the closed container and to contact the products, which immediately begins the deterioration process of the products. These lids are not constructed so as to enable the expulsion of all air as the lid is forced onto the filled container.